package com.gzdh.dishrecognition.ui.view;

import android.content.Context;
import android.database.DataSetObserver;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.GestureDetector.OnGestureListener;
import android.view.MotionEvent;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.Scroller;

import java.util.LinkedList;
import java.util.Queue;

public class HorizontalListView extends AdapterView<ListAdapter> {

  public boolean mAlwaysOverrideTouch = true;
  protected ListAdapter mAdapter;
  private int mLeftViewIndex = -1;
  private int mRightViewIndex = 0;
  protected int mCurrentX;
  protected int mNextX;
  private int mMaxX = Integer.MAX_VALUE;
  private int mDisplayOffset = 0;
  protected Scroller mScroller;
  private GestureDetector mGesture;
  private Queue<View> mRemovedViewQueue = new LinkedList<View>();
  private OnItemSelectedListener mOnItemSelected;
  private OnItemClickListener mOnItemClicked;
  private OnItemLongClickListener mOnItemLongClicked;
  private boolean mDataChanged = false;


  public HorizontalListView(Context context, AttributeSet attrs) {
    super(context, attrs);
    initView();
  }

  private synchronized void initView() {
    mLeftViewIndex = -1;
    mRightViewIndex = 0;
    mDisplayOffset = 0;
    mCurrentX = 0;
    mNextX = 0;
    mMaxX = Integer.MAX_VALUE;
    mScroller = new Scroller(getContext());
    mGesture = new GestureDetector(getContext(), mOnGesture);
  }

  @Override
  public void setOnItemSelectedListener(OnItemSelectedListener listener) {
    mOnItemSelected = listener;
  }

  @Override
  public void setOnItemClickListener(OnItemClickListener listener){
    mOnItemClicked = listener;
  }

  @Override
  public void setOnItemLongClickListener(OnItemLongClickListener listener) {
    mOnItemLongClicked = listener;
  }

  private DataSetObserver mDataObserver = new DataSetObserver() {

    @Override
    public void onChanged() {
      synchronized(HorizontalListView.this){
        mDataChanged = true;
      }
      invalidate();
      requestLayout();
    }

    @Override
    public void onInvalidated() {
      reset();
      invalidate();
      requestLayout();
    }

  };
  public boolean onInterceptTouchEvent(MotionEvent ev) {
    getParent().requestDisallowInterceptTouchEvent(true);
    return mGesture.onTouchEvent(ev);
  };
  @Override
  public ListAdapter getAdapter() {
    return mAdapter;
  }

  @Override
  public View getSelectedView() {
    return null;
  }

  @Override
  public void setAdapter(ListAdapter adapter) {
    if(mAdapter != null) {
      mAdapter.unregisterDataSetObserver(mDataObserver);
    }
    mAdapter = adapter;
    mAdapter.registerDataSetObserver(mDataObserver);
    reset();
  }

  private synchronized void reset(){
    initView();
    removeAllViewsInLayout();
        requestLayout();
  }

  @Override
  public void setSelection(int position) {
  }

  private void addAndMeasureChild(final View child, int viewPos) {
    LayoutParams params = child.getLayoutParams();
    if(params == null) {
      params = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
    }

    addViewInLayout(child, viewPos, params, true);
    child.measure(MeasureSpec.makeMeasureSpec(getWidth(), MeasureSpec.AT_MOST),
        MeasureSpec.makeMeasureSpec(getHeight(), MeasureSpec.AT_MOST));
  }



  @Override
  protected synchronized void onLayout(boolean changed, int left, int top, int right, int bottom) {
    super.onLayout(changed, left, top, right, bottom);

    if(mAdapter == null){
      return;
    }

    if(mDataChanged){
      int oldCurrentX = mCurrentX;
      initView();
      removeAllViewsInLayout();
      mNextX = oldCurrentX;
      mDataChanged = false;
    }

    if(mScroller.computeScrollOffset()){
      int scrollx = mScroller.getCurrX();
      mNextX = scrollx;
    }

    if(mNextX <= 0){
      mNextX = 0;
      mScroller.forceFinished(true);
    }
    if(mNextX >= mMaxX) {
      mNextX = mMaxX;
      mScroller.forceFinished(true);
    }

    int dx = mCurrentX - mNextX;

    removeNonVisibleItems(dx);
    fillList(dx);
    positionItems(dx);

    mCurrentX = mNextX;

    if(!mScroller.isFinished()){
      post(new Runnable(){
        @Override
        public void run() {
          requestLayout();
        }
      });

    }
  }

  private void fillList(final int dx) {
    int edge = 0;
    View child = getChildAt(getChildCount()-1);
    if(child != null) {
      edge = child.getRight();
    }
    fillListRight(edge, dx);

    edge = 0;
    child = getChildAt(0);
    if(child != null) {
      edge = child.getLeft();
    }
    fillListLeft(edge, dx);


  }

  private void fillListRight(int rightEdge, final int dx) {
    while(rightEdge + dx < getWidth() && mRightViewIndex < mAdapter.getCount()) {

      View child = mAdapter.getView(mRightViewIndex, mRemovedViewQueue.poll(), this);
      addAndMeasureChild(child, -1);
      rightEdge += child.getMeasuredWidth();

      if(mRightViewIndex == mAdapter.getCount()-1) {
        mMaxX = mCurrentX + rightEdge - getWidth();
      }

      if (mMaxX < 0) {
        mMaxX = 0;
      }
      mRightViewIndex++;
    }

  }

  private void fillListLeft(int leftEdge, final int dx) {
    while(leftEdge + dx > 0 && mLeftViewIndex >= 0) {
      View child = mAdapter.getView(mLeftViewIndex, mRemovedViewQueue.poll(), this);
      addAndMeasureChild(child, 0);
      leftEdge -= child.getMeasuredWidth();
      mLeftViewIndex--;
      mDisplayOffset -= child.getMeasuredWidth();
    }
  }

  private void removeNonVisibleItems(final int dx) {
    View child = getChildAt(0);
    while(child != null && child.getRight() + dx <= 0) {
      mDisplayOffset += child.getMeasuredWidth();
      mRemovedViewQueue.offer(child);
      removeViewInLayout(child);
      mLeftViewIndex++;
      child = getChildAt(0);

    }

    child = getChildAt(getChildCount()-1);
    while(child != null && child.getLeft() + dx >= getWidth()) {
      mRemovedViewQueue.offer(child);
      removeViewInLayout(child);
      mRightViewIndex--;
      child = getChildAt(getChildCount()-1);
    }
  }

  private void positionItems(final int dx) {
    if(getChildCount() > 0){
      mDisplayOffset += dx;
      int left = mDisplayOffset;
      for(int i=0;i<getChildCount();i++){
        View child = getChildAt(i);
        int childWidth = child.getMeasuredWidth();
        child.layout(left, 0, left + childWidth, child.getMeasuredHeight());
        left += childWidth + child.getPaddingRight();
      }
    }
  }

  public synchronized void scrollTo(int x) {
    mScroller.startScroll(mNextX, 0, x - mNextX, 0);
    requestLayout();
  }

  @Override
  public boolean dispatchTouchEvent(MotionEvent ev) {
    boolean handled = super.dispatchTouchEvent(ev);
    handled |= mGesture.onTouchEvent(ev);
    return handled;
  }

  protected boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
        float velocityY) {
    synchronized(HorizontalListView.this){
      mScroller.fling(mNextX, 0, (int)-velocityX, 0, 0, mMaxX, 0, 0);
    }
    requestLayout();

    return true;
  }

  protected boolean onDown(MotionEvent e) {
    mScroller.forceFinished(true);
    return true;
  }

  private OnGestureListener mOnGesture = new GestureDetector.SimpleOnGestureListener() {

    @Override
    public boolean onDown(MotionEvent e) {
      return HorizontalListView.this.onDown(e);
    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
        float velocityY) {
      return HorizontalListView.this.onFling(e1, e2, velocityX, velocityY);
    }

    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2,
        float distanceX, float distanceY) {

      synchronized(HorizontalListView.this){
        mNextX += (int)distanceX;
      }
      requestLayout();

      return true;
    }

    @Override
    public boolean onSingleTapConfirmed(MotionEvent e) {
      for(int i=0;i<getChildCount();i++){
        View child = getChildAt(i);
        if (isEventWithinView(e, child)) {
          if(mOnItemClicked != null){
            mOnItemClicked.onItemClick(HorizontalListView.this, child, mLeftViewIndex + 1 + i, mAdapter.getItemId( mLeftViewIndex + 1 + i ));
          }
          if(mOnItemSelected != null){
            mOnItemSelected.onItemSelected(HorizontalListView.this, child, mLeftViewIndex + 1 + i, mAdapter.getItemId( mLeftViewIndex + 1 + i ));
          }
          break;
        }

      }
      return true;
    }

    @Override
    public void onLongPress(MotionEvent e) {
      int childCount = getChildCount();
      for (int i = 0; i < childCount; i++) {
        View child = getChildAt(i);
        if (isEventWithinView(e, child)) {
          if (mOnItemLongClicked != null) {
            mOnItemLongClicked.onItemLongClick(HorizontalListView.this, child, mLeftViewIndex + 1 + i, mAdapter.getItemId(mLeftViewIndex + 1 + i));
          }
          break;
        }

      }
    }

    private boolean isEventWithinView(MotionEvent e, View child) {
            Rect viewRect = new Rect();
            int[] childPosition = new int[2];
            child.getLocationOnScreen(childPosition);
            int left = childPosition[0];
            int right = left + child.getWidth();
            int top = childPosition[1];
            int bottom = top + child.getHeight();
            viewRect.set(left, top, right, bottom);
            return viewRect.contains((int) e.getRawX(), (int) e.getRawY());
        }
  };



}
